new chickens dont leave the coop????

I posted earlier in Emergencies and Diseases but figured I would post here too as there are some behavorial questions too....

Any help would be greatly appreciated as I am new to chicken keeping this year.

Thank you in advance!!! <3 original post below :

Hello BYC fam!!! ( I apologise in advance for the lengthy post. I feel that the background is important in helping figure out what could be wrong)

So we have three chickens (Buffy, Mo, and Hennie) they are perfect, beautiful, happy, and friendly!!! We were planning on getting more and someone my uncle works with wanted to get rid of his little coop and three chickens (1 year old) We gladly took them and their house in. I cant imagine someone not loving / wanting to keep their babies and knew I could give them a new home / spoil them / love them. (we named them Reggie, Tori, and Marsala) Marsala is a barred rock big and beautiful. Reggie is a brown leghorn large and beautiful. Tori is the runt of the group very small brown leghorn (?) with long spurs. The gentleman we got them from said he never feeds them any treats just feed and water. (Rusty old little waterer gross! threw that out right away!!!)

We got them a week ago... we noticed they were very scared (naturally we uprooted their home) We noticed that they almost NEVER leave the house part of the coop. It is very rare that we catch them in the run (HOW SAD!!! Buffy Mo and Hennie wouldnt be caught dead in their house during the day! There are so man little bugs and worms and pebbles to eat and play with on the ground!) So they have been inside their little house, never leave, never forage. We coaxed them out this weekend with scratch and a head of lettuce (they really liked both!!!!!) The became a bit more friendly ( I think they started to associate me with food and water ) Ill take it!) I noticed that they dont eat nearly as much as Buffy Mo and Hennie... so I started giving them a little extra scratch / lettuce / treats. They drink lots of water!

On Sunday morning I let them free range again... this time it took much less coaxing! I think they are starting to act like real chickens! I noticed Marsala (the adopted barred rock) looked like she had pasty but!!! (shes a grown chicken I didnt think this was possible! I thought it just happened with fuzzy but babies.) So we caught her, and I dissolved the poop with a wet paper towel. It seemed to be around her vent (? nicer way of saying vagina?) but didnt obstruct it. Either way, I made sure she was good and free of any poops & she bocked in thanks. Ran over to the scratch / lettuce gobbled some down and went on her merry way foraging in the yard.

Yesterday (my husbands day to tend chickens) he said Marsala was laying in the coop and didnt come out to forage with the other two. We decided they maybe are not eating enough so we though about giving them a little of the grower food (which Buffy, Mo, and Hennie are still on) in the morning to see if they liked that better / had more interest in it (picky chickens maybe????) But when Joe went to check on them this morning Marsala died. he checked her butt, and body for any visible injuries / problems and couldnt see any issues.

I am worried about Tori and Reggie... (and so glad we didnt introduce them to our other three babies!!!) Do you think Marsala was sick? Possibly backed up with poop? Could Tori and Reggie also be sick? Is this why their appetite is not like the other chickens? Will they be okay just the two of them in their coop / run? Will they be sad without their "Momma Hen" ?

Confine new birds within sight but physically segregated from older/existing birds for several weeks, so they can see and get used to each other but not physically interact. Integrating new birds of equal size works best.

For smaller chicks I used a large wire dog crate right in the coop for the smallers. I removed the crate door and put up a piece of wire fencing over the opening and bent up one corner just enough for the smallers to fit thru but the biggers could not. Feed and water inside the crate for the smallers. Make sure the smallers know how to get in and out of the crate opening before exposing them to the olders. this worked out great for me, by the time the crate was too small for the them to roost in there(about 3 weeks), they had pretty much integrated themselves to the olders.

If you have too many smallers to fit in a crate you can partition off part of the coop with a wire wall and make the same openings for smallers escape.

The more space, the better. Birds will peck to establish dominance, the pecked bird needs space to get away. As long as there's no blood drawn and/or new bird is not trapped/pinned down, let them work it out. Every time you interfere or remove new birds, they'll have to start the pecking order thing all over again.

Multiple feed/water stations. Dominance issues are most often carried out over sustenance, more stations lessens the frequency of that issue.

Places for the new birds to hide out of line of sight and/or up and away from any bully birds.